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Date: Fri, 15 Feb 2002 11:01:28 -0600
From: Bruno Wolff III <bruno@wolff.to>
To: Wei Weng <wweng@kencast.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: create index on function - why?
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On Fri, Feb 15, 2002 at 11:25:40AM -0500,
  Wei Weng <wweng@kencast.com> wrote:
> I can understand the rationale behind creating index on tables, it 
> speeds up the searching.
> 
> But what is the rationale behind creating index on a function? how does 
> it help with the database performance?

If a where clause includes a function reference, than an index on that
function can speed up finding rows that satisfy the where clause.